57715-43-2Relevant academic research and scientific papers
Electroreduction of μ-oxo iron(III) porphyrins adsorbed on an electrode leading to a cofacial geometry for the iron(II) complex: Unexpected active site for the catalytic reduction of O2 to H2O
Oyaizu, Kenichi,Haryono, Agus,Natori, Junichiro,Shinoda, Hiroshi,Tsuchida, Eishun
, p. 1153 - 1163 (2000)
Acidification of a solution of (μ-oxo)bis[(5,10,15,20- tetraphenylporphyrinato)iron(III)] ([{Fe(tpp)}2O], II) in CH2Cl2 produced equimolar amounts of a hydroxoiron(III) complex [(tpp)Fe(III)(OH)] (III) and an iron(III) complex [(tpp)Fe(III)(ClO4)] (IV). The complex IV was isolated as a perchlorate salt, which crystallized in the triclinic space group P1 (2); a = 11.909(3), b = 19.603(4), c = 10.494(3) A, α = 95.74(2)°, β = 107.91(2)°, γ = 89.14(2)°, V = 2319.1(9) A3, Z = 2, D(calc)= 1.328 g cm-3, μ(Mo Kα) = 4.35 cm-1, final R = 0.055 and R(w) = 0.050. The crystal structure of IV revealed that ClO4- is coordinated to the iron atom, which may be driven by the preference of iron(III) to be five coordinate rather than four coordinate. Reduction of the complex II in the presence of acid by electrolysis and/or by a reducing agent, such as sodium dithionite, under argon produced [Fe(II)(tpp)]. The addition of O2 to a solution of [Fe(tpp)] in acidic CH2Cl2 in the presence of an equimolar amount of the reducing agent produced the complex III. When the complex II was adsorbed on an electrode surface and placed in aqueous acidic electrolyte solutions, electroreduction of the adsorbate proceeded according to the half- reaction: [{Fe(tpp)}2O] +2H++2e-→2[Fe(tpp)]+H2O, at 0.031-0.059 pH V (vs. SCE, pH > 1.0). Based on these results, oxo-bridged iron(III) porphyrin dimers were used as electrocatalysts for the reduction of O2. The catalytic reduction of O2 proceeded at potentials in the vicinity of those for II. As a whole, the proportion of H2O as the product increased from 50% for adsorbed [(tpp)Fe(III)Cl] to > 90% for the adsorbed dimer. Thus, electroreduction of the dimer adsorbed on a carbon electrode immersed in aqueous acid produced two solid state, cofacially fixed iron(II) porphyrin molecules: [PFe(III)OFe(III)P](ad)+2H++2e-→[PFe(II) Fe(II)P](ad)+H2O (P = porphyrin dianion). Coordination of molecular oxygen to the adjacent two iron(II) centers under acidic conditions allowed formation of O2-bridged iron(III) porphyrin [PFe(III)(O2) Fe(III)P](ad) at the electrode surface. Electroreduction of the adsorbate under acidic conditions produced H2O and allowed the reformation of [PFe(II) Fe(II)P](ad). The implication is that the electroreduction of the adsorbed oxo-bridged dimer gives a cofacial geometry for PFe(II) on the electrode, facilitating the coordination and subsequent splitting of O2.
[Fe(TPP)(4-MePip)2]: An axially compressed bis(secondary amine) complex of an iron(II) porphyrin
Munro, Orde Q.,Ntshangase, Mthembeni M.
, p. m224-m227 (2003)
The low-spin iron(II) ion of bis(4-methylpiperidine)(5,10,15,-20-tetraphenylporphyrinato)iron(II), [Fe(TPP)(4-MePip)2], where TPP is 5,10,15,20-tetraphenylporphyrinate (C44H28N4) and 4-MePip is 4-methylpiperidine (C6H13N), is located at a center of inversion, and there is one molecule in the triclinic unit cell. The axial 4-MePip ligands adopt a chair conformation and the α-C atoms are oriented at angles of 21.2 (2) and 32.8 (2)° relative to the closest porphyrin N atoms. The equatorial Fe-NTPP distances are 1.998 (2) and 1.990 (2) A. while the axial Fe-N distance is 2.107 (2) A. The relatively short axial coordination distance reflects compression of the molecule along its principal axis by intermolecular non-bonded interactions.
Effect of Axial Coordination of Iron Porphyrin on Their Nanostructures and Photocatalytic Performance
Tian, Xuemin,Lin, Chensheng,Zhong, Zhou,Li, Xiaoxin,Xu, Xiao,Liu, Jingjing,Kang, Longtian,Chai, Guoliang,Yao, Jiannian
, p. 3279 - 3287 (2019)
Enough exposure of an active face is a key factor of nanocatalysis for sustainable energy conversion. Here, we exhibit the effect of axial coordination of organic metal complex molecules on the morphology evolution and photocatalytic hydrogen evolution (PHE) activity of organic nanocrystals (ONCs). The three series of iron porphyrin (FeTPPX, X = Cl, O, and OH) ONCs are controllably synthesized via the cetyltrimethylammonium bromide (CTAB)-assisted chemical reaction at different pH values. The uniform zero-dimensional FeTPPCl ONCs, ultrafine one-dimensional [FeTPP]2O ONCs with a diameter of ～35 nm, and ultrathin two-dimensional FeTPPOH·H2O ONCs with the thickness of a crystal cell (4). The mechanism of morphology evolution is carefully investigated, revealing the synergistic effect of the axial ligand of FeTPPX and CTAB on the exposure of the hydrophilic active face parallel to the porphyrin ring. Size-, shape-, and axial ligand-dependent photocatalysis can be clearly observed. Without using a cocatalyst, the FeTPPOH·H2O ultrathin nanoflakes display the highest PHE rate (～0.75 mmol/h/g), followed by FeTPPCl octahedrons (～0.48 mmol/h/g) and [FeTPP]2O ultrafine nanorods (～0.20 mmol/h/g). This work provides a new strategy to apply the conjugated organic compounds in nanocatalysis.
The controllable synthesis of ultrafine one-dimensional small-molecule semiconducting nanocrystals in surfactant-assisted wet chemical reactions and their confinement effect
Pan, Jiannan,Kang, Longtian,Huang, Ping,Jia, Ziyan,Liu, Jingjing,Yao, Jiannian
, p. 6377 - 6385 (2017/07/11)
One-dimensional (1D) small-molecule semiconducting nanostructures (NSs) have attracted more and more attention due to their unique structures and photoelectric properties. However, the preparation of real ultrafine 1D organic nanocrystals (ONCs), in which the intermolecular charge transfer (CT) is confined to a 1D direction, is still a huge challenge. Here, we report a facile way to controllably synthesize uniform 1D ONCs of μ-oxo dimeric iron(iii) porphyrin [(FeTPP)2O] in a cetyltrimethyl ammonium bromide (CTAB)-assisted wet chemical reaction (WCR). In this work, the shape evolution of the (FeTPP)2O NSs was shown by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Interestingly, the regularity and aspect ratio of the (FeTPP)2O 1D NCs increased with time, while their diameters decreased. Further experiments proved that this was closely associated to the reconstruction of the CTAB micelles. After optimizing the experimental conditions, we not only synthesized uniform 1D ONCs with a width of ～28 nm and/or an aspect ratio of ～37, but also obtained 2D ONCs with a thickness of about 10 nm. Here, the finest 1D ONCs that we have seen to date have been prepared. The corresponding UV-vis absorption and photoluminescence (PL) spectra are enhanced with a decrease in the diameter and an increase in the aspect ratio of (FeTPP)2O 1D ONCs with high crystallinity, which clearly shows the first report of the confinement effect of the intermolecular CT state in 1D ONCs. This work paves a new route to prepare 1D ONCs and provides us with a chance to further understand and apply the intermolecular CT in 1D organic photoelectrical devices.
Efficient reduction of dioxygen with ferrocene derivatives, catalyzed by metalloporphyrins in the presence of perchloric acid
Fukuzumi, Shunichi,Mochizuki, Seiji,Tanaka, Toshio
, p. 2459 - 2465 (2008/10/08)
Reduction of dioxygen with ferrocene derivatives (Fc) is catalyzed by metalloporphyrins (MTPP+: M = Co, Fe, Mn; TPP = tetraphenylporphyrin) or Co(TIM)3+ (TIM: a tetraaza macrocyclic ligand) in the presence of HClO4 in acetonitrile (MeCN). Electron transfer from Fc to MTPP+ is the rate-determining step for the MTPP+-catalyzed oxidation of Fc by dioxygen, when the rate is independent of the concentration of dioxygen or HClO4. On the other hand, the rate of electron transfer from Fc to Co(TIM)3+ is accelerated by the presence of HClO4 and dioxygen. The rates of these electron-transfer reactions are discussed in light of the Marcus theory of electron transfer to distinguish between outer-sphere and inner-sphere electron-transfer processes. The strong inner-sphere nature of metalloporphyrins in the electron-transfer reactions with dioxygen in the presence of HClO4 plays an essential role in the catalytic reduction of dioxygen.
Reaction of certain nitrogen oxides with iron(III) porphyrin μ-oxo complexes
Settin, Marc F.,Fanning, James C.
, p. 1431 - 1435 (2008/10/08)
The nitrogen oxides NO, N2O4, and N2O3 and the μ-oxo complexes [Fe(TPP)]2O and [Fe(OEP)]2O, where TPP and OEP are the dianions of meso-tetraphenylporphine and octaethylporphyrin, respectively, were reacted in toluene in the absence of O2. [Fe(TPP)]2O was reacted with the nitrogen oxides in dimethylacetamide (DMA). All of the reactions were followed by changes in the electronic spectra. The NO reaction with [Fe(TPP)]2O in toluene yielded a solid product, Fe(TPP)(NO)(NO2)·C7H8·2H 2O. The N2O4 and the N2O3 reactions in toluene produced Fe(TPP)NO3 and Fe(OEP)NO3, while in DMA these reactions gave an equilibrium amount of Fe(TPP)(DMA)x+, the solvated complex.
Electrochemical Synthesis and Characterization of the Single-Electron Oxidation Products of Ferric Porphyrins
Phillippi, Martin A.,Goff, Harold M.
, p. 6026 - 6034 (2007/10/02)
High-spin iron(III) porphyrins are oxidized by electrochemical and selected chemical methods.Both monomeric chloro complexes and μ-oxo dimeric species have been examined.Products are isolated as perchlorate salts in analytically pure form in favorable cases.Contrary to previous interpretations, the singly oxidized species are better formulated as iron(III) porphyrin ?-cation radicals rather than as iron(IV) complexes.This finding is based on electrochemical measurements, electronic absorption spectra, NMR spectra, infrared spectra, and Moessbauer measurements.Oxidation potentials for diverse anionic complexes of iron(III) tetraphenylporphyrin are essentially constant at 1.10+/-0.02 V (SCE), suggestive of porphyrin-centered rather than metal-centered oxidation.Electronic absorption spectra exhibit broad bands at long wavelength, not unlike those for known ? radicals.Unusually large NMR paramagnetic shifts for phenyl protons of oxidized iron tetraphenylporphyrin derivatives are rationalized by proton-radical couplings previously measured for zinc a2u porphyrin radicals.The oxidized iron octaethylporphyrin complex is better described as an a1u species.Efficient relaxation of spin by the paramagnetic iron center permits well-resolved NMR spectra.Infrared spectra serve to demonstrate integrity of the oxo linkage in oxidized μ-oxo dimers.A new absorption band near 1280 cm-1 is seemingly diagnostic of porphyrin-centered oxidation of tetraphenylporphyrin metal complexes.Moessbauer spectra reveal little perturbation of charge at the iron center associated with oxidation.Isomer shift values near 0.4 mm/s (iron metal) resemble those for parent iron(III) complexes.Solution magnetic moment measurements yield an unusual 5.5-μB value for oxidized iron tetraphenylporphyrin and iron octaethylporphyrin derivatives.Absence of metal-centered oxidation for weak-field anionic complexes indirectly supports the necessity of an oxo or hydroxo ligand in iron(IV) states of hemoproteins.
